Acquired immunity against micro-organisms 263 



a more extended development. Nor has any one else attempted to 

 defend it. 



It is probable that in certain special cases the immobilisation of very 

 motile bacteria and their agglutination into clumps may facilitate the 

 reaction of the animal organism, especially the rapidity of phagocy- 

 tosis. Thus, Besredka 1 observed that guinea-pigs when inoculated 

 with typhoid bacilli that had previously been mixed with the blood 

 serum of normal animals survived. The most active amongst these 

 serums was ox serum heated to 60 C. Guinea-pigs furnished a 

 serum which was much less active. The resistance of guinea-pigs, 

 inoculated into the peritoneal cavity, was in direct ratio to the 

 agglutinated condition of the bacilli. Besredka lays stress on the 

 facility with which the bacilli, when agglomerated into large clumps, 

 were ingested by the phagocytes, and suggests that there is a certain 

 stimulating action of the serums on the leucocytes. When he in- 

 jected into guinea-pigs a mixture of typhoid bacilli and guinea-pig's 

 serum, made immediately before injection, his animals died from 

 infection. But when he left the bacilli for some time in contact 

 with the guinea-pig's serum outside the body, and did not inject 

 the mixture until after agglutination was complete, the inoculated 

 animals usually survived. This experiment indicates the part played 

 by agglutination in the resistance offered by the animal, and at the 

 same time proves that in the body of the guinea-pig the agglomera- 

 tion of the micro-organisms into clumps does not take place to the [277] 

 same degree as in the serum prepared in, and left in contact with, 

 the air. 



In any case, the data collected by Besredka cannot be put 

 forward as an argument in favour of the essential part played by 

 agglutination in acquired immunity, nor can they weaken the facts 

 indicated as to the absence of agglutinative power in examples of 

 acquired immunity and as to the virulence of the agglutinated micro- 

 organisms. The part played by agglutination in this immunity is 

 merely accidental and subordinate. 



Special researches have been carried out with the object of de- 

 fining, exactly, the origin of agglutinins in the body of an animal 

 that has acquired immunity. Observers are unanimous in recognising 

 that, of all parts of the organism, the blood is richest in agglutinin. 

 This substance is found in the blood serum as well as in the plasma. 

 From this (corroborated by the agglutinative property of other 

 1 Ann. de FInst. Pasteur, Paris, 1901, t. xv, p. 209. 



